The present invention provides a liquid formulation of a distyrylbiphenyl fluorescent whitening agent of the formula 
for imparting a particularly white aspect to detergent compositions.
As normally manufactured, compounds of Formula (1) have a yellowish tinge which, depending upon the method of manufacture, can impart an undesirable discolouration to the finished detergent.
Surprisingly, it has now been found that a specific formulation of compound (1) is able to overcome this disadvantage.
Accordingly, the present invention describes a liquid fluorescent whitening agent formulation comprising:
a) 10 to 20% of a compound of Formula (1) in which R1 represents hydrogen, 1-5 C-alkyl, 1-5 C-alkoxy or halogen, M represents hydrogen, an alkaline- or alkaline earth-metal, or ammonium;
b) 20 to 50% of a non-ionic surfactant;
c) 20 to 40% of a polyhydroxy compound;
d) 0 to 20% of a glycol compound and
e) 1 to 50% water.
Preferably, the optical whitening agent is of the formula 
the compound of formula (2) being most preferred.
The non-ionic surfactant, component b) of the formulation is preferably an alkoxylated fatty acid alcohol, especially ethoxylated and is, more preferably, a C8-C18-fatty acid alcohol which is ethoxylated with between 3 and 20 moles of ethylene oxide, a C11-C13-fatty acid alcohol which is ethoxylated with between 3 and 20 moles of ethylene oxide being most preferred, whereby a C13-fatty acid alcohol which is ethoxylated with 9 moles of ethylene oxide (Marlipal 013/90) being the component of choice.
The polyhydroxy compound, component c) of the formulation is, preferably, a triol such as 1,2,6-hexanetriol, glycerine or an oligomer of glycerine such as a di-, tri- or polyglycerine, glycerine being most preferred.
The glycol compound, component d) of the formulation is, for example, ethylene glycol, diethylene glycol, propylene glycol or hexylene glycol, the hexylene glycol 2-methyl-2,4-pentanediol and 1,2-propylene glycol being preferred.
A preferred formulation comprises
a) 10 to 20% of the compound of formula (2);
b) 20 to 50% of a C11-C13fatty acid alcohol which is ethoxylated with between 3 and 20 moles of ethylene oxide;
c) 20 to 40% of glycerine;
d) 0 to 20% of ethylene glycol, 1,2-propylene glycol or 2-methyl-2,4-pentanediol and
e) 1 to 50% of water, whereby a formulation comprising
a) 10 to 20% of the compound of formula (2);
b) 20 to 50% of a C13-fatty acid alcohol which is ethoxylated with 9 moles of ethylene oxide;
c) 20 to 40% of glycerine;
d) 5 to 20% of 1,2-propylene glycol or 2-methyl-2,4-pentanediol and
e) 10 to 40% of water is particularly preferred.
When, in formula (1), R1 represents 1-5 C-alkyl, these may be methyl, ethyl, n- or isopropyl, n-, sec-, or t-butyl, n-pentyl, iso-amyl or sec-amyl groups. When, in formula (1), R1 represents 1-5 C-alkoxy, these may be methoxy, ethoxy, n- or isopropoxy, n-, sec-, or t-butoxy, n-pentyloxy, iso-amyloxy or sec-amyloxy groups. When, in formula (1), R1 represents halogen, these may be fluorine, chlorine, bromine, or iodine, preferably chlorine.
Optional auxiliaries which may be present in the formulation of the present invention include stabilisers which are effective in adjusting the flow properties of the formulation, anti-foam agents, alkaline agents, fabric softeners, anti-redeposition agents, antioxidants, auxiliary builders such as polyacrylic acid and fragrances.
Examples of such stabilisers include, e.g., kaolin, an Mg/Al silicate, especially bentonite, montmorillonite, a zeolite or a highly dispersed silicic acid.
The formulation of the present invention may be produced by mixing the components a) to e) together with any optional auxiliaries, and homogenising the mixture so obtained, preferably at an elevated temperature, e.g. at 40-100xc2x0 C. Mixing is conveniently effected by a suitable stirring device.
The resulting formulation is normally a clear and stable solution. On occasion, however, it may be necessary to filter the formulation in order to remove minor amounts of insoluble components.
The formulation of the present invention is particularly suitable for incorporation into a dry detergent composition, conveniently by adding the required amount of the formulation of the present invention to a dry detergent composition and then homogenising the mixture so obtained. The formulation of the present invention may also be used, however, for the production of liquid detergents by adding the required amount of the formulation of the present invention to a liquid detergent composition and then homogenising the mixture so obtained. The liquid formulation of the invention is also characterized by its excellent stability under cold storage conditions.